<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>盒子模型</title>
    <style>
        div{
            width:200px;
            height: 100px;
            /* box-sizing: border-box; 指定宽度和高度是盒子高度 */
            background-color: aquamarine;

            padding:20px,20px;
            border:1px,solid red;
            margin:30px;
        }
    </style>
</head>
<body>
    <div>a a a a a a a a &nbsq</div>
</body>
</html>